Ink-jet receptor sheet containing nitrile polymer

ABSTRACT

A substrate for ink-jet printing which is coated or impregnated with a water dissipatable nitrile polymer having a Mn of less than 25,000 comprising 5 to 70% w/w of nitrile monomers. Also processes for ink-jet printing and printed substrates.

[0001] This invention relates to ink receptive substrates which areparticularly suitable for use in ink-jet printing (IJP) and to ink-jetprinting methods using these substrates.

[0002] IJP is a non-impact printing technique in which droplets of inkare ejected through a fine nozzle onto a substrate without bringing thenozzle into contact with the substrate. There are many demandingperformance requirements for ink-jet prints. For example they shouldprovide sharp, non-feathered images and have good water-fastness,light-fastness and optical density. The provision of images withexcellent light-fastness is particularly important in photorealisticquality printing. Prints are often exposed to daylight for long periodsand there is a need for the image to have as good light-fastness aspossible. To achieve an acceptable level of performance when compared tosilver halide photography the nature of both the ink used to form theimage and the substrate on which the image is formed must be carefullycontrolled. To this end we have found that the incorporation of certainnitrite polymers into substrates for IJP provides prints that exhibitenhanced light-fastness.

[0003] According to the present invention there is provided a substratefor ink-jet printing which is coated or impregnated with awater-dissipatable nitrite polymer having a Mn of less than 25,000comprising 5 to 70% w/w of nitrile monomers.

[0004] The substrate is preferably a coated or uncoated paper, plastic,textile, metal or glass, more preferably a coated or uncoated paper,overhead projector slide or a textile material, especially a coated oruncoated paper.

[0005] Preferred papers are plain or treated papers which may have anacid, alkaline or neutral character. Examples of commercially availabletreated papers include HP Premium Coated Paper (available from HewlettPackard Inc.), HP Photopaper (available from Hewlett Packard Inc.),Stylus Pro 720 dpi Coated Paper, Epson Photo Quality Glossy Film(available from Seiko Epson Corp.), Epson Photo Quality Glossy Paper(available from Seiko Epson Corp.), Canon HR 101 High Resolution Paper(available from Canon), Canon GP 201 Glossy Paper (available fromCanon), and Canon HG 101 High Gloss Film (available from Canon). Thesepapers may easily be modified to include nitrite polymer during theirmanufacture. For example, one may perform the process described in PPG'sU.S. Pat. No. 5,880,196, Example 1, or U.S. Pat. No. 5,804,293, Examples1 to 110, or in the Examples of U.S. Pat. No. 4,892,779, modified suchthat the nitrile polymer is included as an ingredient in the coatingcompositions described in these Examples.

[0006] Preferred textile materials are natural, synthetic andsemi-synthetic materials. Examples of preferred natural textilematerials include wool, silk, hair and cellulosic materials,particularly cotton, jute, hemp, flax and linen. Examples of preferredsynthetic and semi-synthetic materials include polyamides, polyesters,polyacrylonitriles and polyurethanes.

[0007] Preferably the nitrile polymer is obtainable by polymerisation ofone or more olefinically unsaturated nitrile monomers, optionally in thepresence of olefinically unsaturated monomers which are free fromnitrile groups. More preferably the water-dissipatable nitrite polymerhas been obtained from the polymerisation of acrylonitrile and/ormethacrylonitrile with one or more olefinically unsaturated monomershaving water dispersing groups, optionally in the presence of one ormore olefinically unsaturated monomers which are free from waterdispersing groups.

[0008] The nitrite monomers may be chemically different (e.gacrylonitrile and methacrylonitrile) or they may be the same (e.gmethacrylonitrile may be the only nitrile monomer in the nitritepolymer).

[0009] Preferably the nitrite polymer comprises 10 to 60%, morepreferably 20 to 50% w/w of a nitrite monomer. The percentage nitritemonomer in the polymer is calculated on a weight basis by dividing thetotal weight of nitrite monomers used to make the polymer by the totalweight of all monomers used to make the polymer and multiplying theresultant figure by 100.

[0010] Preferably the nitrite polymer has a number average molecularweight (Mn) of less than 20,000. The Mn of the nitrite polymer may bemeasured by gel permeation chromatography (“gpc”).

[0011] The gpc method used for determining Mn preferably comprisesapplying the nitrite polymer to a chromatography column packed withcross-linked polystyrene/divinyl benzene, eluting the column withtetrahydrofuran at a temperature of 40° C. and assessing the Mn of thenitrite polymer compared to a number of a polystyrene standards of aknown Mn. Suitable cross-linked polystyrene/divinyl benzenechromatography columns are commercially available from PolymerLaboratories.

[0012] If the gpc method for determining Mn does not work for anyreason, for example the nitrite polymer has an unexpected interactionwith the gpc column and so gives an unrealistic result, the Mn may bedetermined using alternative methods, for example by vapour phaseosmometry.

[0013] The nitrite polymer preferably has an acid value of from 0 to 750mgKOH/g, more preferably 0 to 450 mgKOH/g, especially 0 to 225 mgKOH/g.

[0014] The water-dissipatable polymer preferably carrieswater-dispersing groups to provide the facility of self-dispersibilityor solubility in water. The dispersing groups may be ionic, non-ionic ora mixture of ionic and non-ionic dispersing groups. Preferred ionicdispersing groups include cationic quaternary ammonium groups and acidgroups, for example phosphoric acid groups, sulphonic acid groups andcarboxylic acid groups.

[0015] The dispersing groups may be incorporated into the nitrilepolymer in the form of monomers or oligomers bearing the appropriatedispersing group. One may also react a nitrite polymer that is notwater-dissipatable with monomers or oligomers which make the nitritepolymer water-dissipatable.

[0016] The acid groups may be subsequently, or during formation of thepolymer, fully or partially neutralised with a base containing acationic charge to give a salt. If acid dispersing groups are used incombination with a non-ionic dispersing group, neutralisation may not berequired. The conversion of any free acid groups into the correspondingsalt may be effected during the preparation of the nitrile polymerand/or during the preparation of a solution or dispersion of the nitrilepolymer.

[0017] Preferably the base used to neutralise any acid dispersing groupsis ammonia, an amine or an inorganic base. Suitable amines includetertiary amines, for example triethylamine or triethanolamine. Suitableinorganic bases include alkaline hydroxides and carbonates, for examplelithium hydroxide, sodium hydroxide, or potassium hydroxide. Aquaternary ammonium hydroxide, for example N⁺(CH₃)₄OH⁻, can also beused. Generally a base is used which gives the required counter iondesired for the composition which is prepared from the nitrile polymer.For example, suitable counter ions include Li⁺, Na⁺, K⁺, NH₄ ⁺ andsubstituted ammonium salts (including tetra substituted amines, e.g.(CH₃)₄N⁺).

[0018] Non-ionic dispersing groups may be in-chain, pendant or terminalgroups. Preferably non-ionic dispersing groups are pendantpolyoxyalkylene groups, more preferably polyoxyethylene groups. Thenon-ionic groups may be introduced into the nitrile polymer in the formof a compound bearing non-ionic dispersing groups and at least one(although preferably only one) copolymerisable olefinically unsaturatedgroup.

[0019] The nature and level of dispersing groups in the nitrile polymerinfluences whether a solution, dispersion, emulsion or suspension isformed on dissipation of the nitrile polymer.

[0020] The dispersing group content of the nitrile polymer may varywithin wide limits but is preferably sufficient to enable the nitrilepolymer to form stable compositions in water and aqueous media.Preferably the monomer bearing the dispersing group comprises 1-40%,more preferably 5-35% by weight of the total weight of monomers used tomake the nitrile polymer.

[0021] The nitrile polymer may be prepared in a conventional manner bypolymerising nitrile(s) and the olefinically unsaturated monomers,.Temperatures of from 20° C. and 180° C. are preferred. Thepolymerisation may be continued until reaction between the monomers iscomplete.

[0022] In one embodiment the nitrile polymer may be prepared bypolymerising a nitrile monomer, an oligomer having water dispersinggroups and one olefinically unsaturated terminal group in the presenceof one or more olefinically unsaturated monomers which are free fromwater dispersing groups and/or olefinically unsaturated monomers havingwater dispersing groups. Alternatively a nitrile oligomer which is freefrom water dispersing groups may be polymerised in the presence of oneor more olefinically unsaturated monomers having water dispersinggroups.

[0023] Preferred polymerisation methods include solution polymerisation,emulsion polymerisation, suspension polymerisation andsolution/dispersion polymerisation, such general methods are well knownin the art.

[0024] If desired an initiator may be used to assist nitrile polymerformation. Suitable initiators are free-radical generators. Examples ofcatalysts include azobis compounds, peroxides, hydroperoxides, redoxcatalysts, etc., for example, potassium persulfate, ammonium persulfate,tert-butyl peroctoate, benzoyl peroxide, isopropyl percarbonate,2,4-dichlorobenzoyl peroxide, methyl ethyl ketone peroxide, cumenehydroperoxide, dicumyl peroxide, azobisisobutyronitrile,azobis(2-amidino-propane)hydrochloride and the like.

[0025] Typically 0.05 to 5% by weight of initiator is used relative tothe total weight of the monomers. Preferably the polymerisation isperformed in the presence of an emulsifying agent.

[0026] The Mn of the nitrile polymer may be controlled by the additionof chain transfer agents and/or through the adjustment of the ratio ofthe concentration of monomers relative to the concentration of initiatorduring the course of the polymerisation. Typical chain transfer agentsare thiols, halocarbons and cobalt macrocycles.

[0027] The nitrile polymer is preferably purified before it is used, forexample the nitrile polymer dissipated in water may be purified byion-exchange, filtration, reverse osmosis, dialysis, ultra-filtration ora combination thereof. In this way one may remove co-solvents used forthe polymerisation, low molecular weight salts, impurities and freemonomers Preferred olefinically unsaturated nitrile monomers includeacrylonitrile, methacrylonitrile, allyl cyano acetate, 2-cyano ethylacetate, allyl cyanide, alkyl α-cyanoacrylates, especiallymethyl-α-cyanoacrylates, cyano-N-vinyl acetamide, allyl oxypropionitrile, N,N-diallyl amino acetonitrile, N,N-diallyl aminopropionitrile, cinnamonitrile, 2-phenyl-1,1-dicyanoethylene,crotononitrile, 1 and 2-cyanol1,3-butadienes especially 1 cyanoprene,fumaronitrile, vinylidene cyanide, 2-cyano ethyl methacrylate, vinylbenzyl cyanide, cyano ethoxy ethyl acrylate and 4-cyanostyrene.Acrylonitrile and methacrylonitrile are especially preferred.

[0028] Preferred olefinically unsaturated monomers providing ionicdispersing groups include acrylic acid, methacrylic acid, itaconic acid,maleic acid, monoalkyl itaconates (for example, monomethyl maleate,monoethyl maleate, monobutyl maleate and monooctyl maleate), citraconicacid, styrenesulfonic acid, vinylbenzylsulfonic acid, vinylsulfonicacid, acryloyloxyalkyl sulfonic acids (for example, acryloyloxymethylsulfonic acid, acryloyloxyethyl sulfonic acid, acryloyloxypropylsulfonic acid and acryloyloxybutyl sulfonic acid), methacryloyloxymethylsulfonic acid, methacryloyloxyethyl sulfonic acid, methacryloyloxypropylsulfonic acid and methacryloyloxybutyl sulfonic acid),2-acrylamido-2-alkylalkane sulfonic acids (for example,2-acrylamido-2-methylethanesulfonic acid,2-acrylamido-2-methylpropanesulfonic acid and2-acrylamido-2-methylbutane sulfonic acid),2-methacrylamido-2-alkylalkane sulfonic acids (for example,2-methacrylamido-2-methylethanesulfonic acid,2-methacrylamido-2-methylpropanesulfonic acid and2-methacrylamino-2-methylbutanesulfonic acid),mono-(acryloyloxyalkyl)phosphates (for example,mono(acryloyloxyethyl)phosphate and mono(3-acryloyloxypropyl)phosphates)and mono(methacryloyloxyalkyl)phosphates (for example,mono(methacryloyloxyethyl)phosphate andmono(3-methacryloyloxypropyl)phosphate).

[0029] Preferred olefinically unsaturated monomers providing non-ionicdispersing groups include alkoxy polyethylene glycol (meth)acrylates,preferably having a number average molecular weight of from 350 to 2000.Examples of such monomers which are commercially available includeω-methoxypolyethylene glycol acrylate (mean polymerisation degree ofpolyethylene glycol is about 9) and diethylene glycol vinyl ether.Preferred olefinically unsaturated monomers which are free fromdispersing groups include alkyl(meth)acrylates, optionally substitutedstyrenes, methacrylamides, allyl compounds, vinyl ethers, vinyl ketones,vinyl halides, olefins and unsaturated nitriles.

[0030] Preferred alkyl(meth)acrylates contain less than twenty carbonatoms. Examples include methyl acrylate, ethyl acrylate, n-propylacrylate, isopropyl acrylate, n-butyl acrylate, isobutyl, sec-butylacrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octylacrylate, tert-octyl acrylate, 2-phenoxyethyl acrylate, 2-chloroethylacrylate, 2-bromoethyl acrylate, 4-chlorobutyl acrylate, cyanoethylacrylate, 2-acetoxyethyl acrylate, dimethylaminoethyl acrylate, benzylacrylate, methoxybenzyl acrylate, 2-chlorocyclohexyl acrylate, acylate,cyclohexyl acylate, furfuryl acrylate, tetrahydrofurfuryl acrylate,phenyl acrylate, hydroxyethyl(methyl)acrylate, hydroxypropyl(meth)acrylate, 5-hydroxypentyl acrylate, 2,2-dimethyl-3-hydoxypropylacrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate,2-ethoxyethyl acrylate, 2-iso-propoxyethyl acrylate, 2-butyoxyethylacrylate, 2-(2-methoxyethoxy)ethyl acrylate, 2-(2-butoxyethoxy)ethylacrylate, 1-bromo-2-methoxyethyl acrylate, 1,1-dichloro-2-ethoxyethylacrylate, methyl methacrylate, ethyl methacrylate, n-propylmethacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutylmethacrylate, sec-butyl methacrylate, amyl methacrylate, hexylmethacrylate, cyclohexyl methacrylate benzylmethacrylate, chlorobenzylmethacrylate, octyl methacrylate, N-ethyl-N-phenylaminoethylmethacrylate, 2-(3-phenylpropyloxy)ethyl methacrylate,dimethylaminophenoxyethyl methacrylate and furfuryl methacrylate.

[0031] Preferred optionally substituted styrenes include styrene,methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene,diethylstyrene, isopropylstyrene, butylstyrene, hexylstyrene,cyclohexylstyrene, decylstyrene, chloromethylstyrene,trifluoromethylstyrene, ethoxymethylstyrene, acetoxymethylstyrene,methoxystyrene, 4-methoxy-3-methylstyrene, dimethoxystyrene,chlorostyrene, dichlorostyrene, trichlorostyrene, tetrachlorostyrene,pentachlorostyrene, bromostyrene, dibromostyrene, iodostyrene,trifluorostyrene and 2-bromo-4-tri-fluoromethylstyrene.

[0032] Preferred methacrylamides contain less than 12 carbon atoms.Examples include methylmethacrylamide, tert-butylmethacrylamide,tert-octylmethacrylamide, benzylmethacrylamide,cyclohexylmethacrylamide, phenylmethacrylamide, dimethylmethacrylamide,dipropylmethacrylamide, hydroxyethyl-N-methylmethacrylamide,N-methylphenylmethacrylamide, N-ethyl-N-phenylmethacrylamide andmethacrylhydrazine.

[0033] Preferred allyl compounds include allyl acetate, allyl caproate,allyl caprylate, allyl laurate, allyl palmitate, allyl stearate, allylbenzoate, allyl acetoacetate, allyl lactate, allyloxyethanol, allylbutyl ether and allyl phenyl ether.

[0034] Preferred vinyl ethers contain less than 20 carbon atoms.Examples include methyl vinyl ether, butyl vinyl ether, hexyl vinylether, octyl vinyl ether, decyl vinyl ether, ethylhexyl vinyl ether,methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethyl vinylether, 1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinylether, hydroxyethyl vinyl ether and dimethylaminoethyl vinyl ether.

[0035] Preferred vinyl ketones contain less than 12 carbon atoms.Examples include methyl vinyl ketone, phenyl vinyl ketone andmethoxyethyl vinyl ketone.

[0036] Preferred vinyl halides include vinyl chloride, vinylidenechloride and chlorotrifluoro ethylene.

[0037] Preferred olefins include unsaturated hydrocarbons having lessthan 20 carbon atoms. Examples include dicyclopentadiene, ethylene,propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene,1-octene, 1-decene, 5-methyl-1-nonene, 5,5-dimethyl-1-octene,4-methyl-1-hexene, 4,4-dimethyl-1-pentene, 5-methyl-1-hexene,4-methyl-1-heptene, 5-methyl-1-heptene, 4,4-dimethyl-1-hexene,5,5,6-trimethyl-1-heptene, 1-dodecene and 1-octadecene.

[0038] The preferred olefinically unsaturated monomers which are freefrom dispersing groups are the alkyl (meth)acrylates containing lessthan 20 carbon atoms, especially those specifically listed above.

[0039] Preferred methods for coating or impregnating the substrate withthe nitrile polymer include, for example, dip coating, reverse rollercoating, K-bar coating, spraying and ink-jet printing. The substrate maybe coated with a plurality of layers, each layer comprising either thesame or a different composition.

[0040] When the substrate is coated or impregnated with the nitrilepolymer in the form of a mixture with a liquid medium it is preferredthat the coated or impregnated substrate is dried before ink is applied.Any suitable drying method may be used, for example hot air drying.

[0041] Preferably the substrate is obtainable by impregnating or coatingwith a composition comprising a water dissipatable nitrile polymerhaving a Mn of less than 25,000 comprising 5 to 70% w/w of nitrilemonomers, a liquid medium and optionally a binder. The liquid mediumpreferably comprises water or a mixture of water and organic solvent.Preferred organic solvents are water-miscible organic solvents,water-immiscible organic solvents and mixtures thereof.

[0042] Suitable water-miscible organic solvents include C₁₋₅-alkanols,e.g. methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol,tert-butanol and isobutanol; amides, e.g. dimethylformamide anddimethylacetamide; ketones and ketone alcohols, e.g. acetone anddiacetone alcohol; C₂₋₄-ether, e.g. tetrahydrofuran and dioxane;alkylene glycols or thioglycols containing a C₂-C₆ alkylene group, e.g.ethylene glycol, propylene glycol, butylene glycol, pentylene glycol andhexylene glycol; poly(alkylene-glycol)s and thioglycol)s, e.g.diethylene glycol, thiodiglycol, polyethylene glycol and polypropyleneglycol; polyols, e.g. glycerol and 1,2,6-hexanetriol; and lower alkylglycol and polyglycol ethers, e.g. 2-methoxyethanol,2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy) ethanol,2-(2-butoxyethoxy)ethanol, 3-butoxypropan-1-ol,2-[2-(2-methoxyethoxy)-ethoxy]ethanol,2-[2-(2-ethoxyethoxy)ethoxy]-ethanol; cyclic esters and cyclic amides,e.g. optionally substituted pyrrolidones; sulpholane; and mixturescontaining two or more of the aforementioned water-miscible organicsolvents. Preferred water-miscible organic solvents are C₁₋₆-alkyl monoethers of C₂₋₆-alkylene glycols and C₁₋₆-alkyl mono ethers ofpoly(C₂₋₆-alkylene glycols).

[0043] Suitable water-immiscible organic solvents include aromatichydrocarbons, e.g. toluene, xylene, naphthalene, tetrahydronaphthaleneand methyl naphthalene; chlorinated aromatic hydrocarbons, e.g.chlorobenzene, fluorobenzene, chloronaphthalene and bromonaphthalene;esters, e.g. butyl acetate, ethyl acetate, methyl benzoate, ethylbenzoate, benzyl benzoate, butyl benzoate, phenylethyl acetate, butyllactate, benzyl lactate, diethyleneglycol dipropionate, dimethylphthalate, diethyl phthalate, dibutyl phthalate, di (2-ethylhexyl)phthalate; alcohols having six or more carbon atoms, e.g. hexanol,octanol, benzyl alcohol, phenyl ethanol, phenoxy ethanol, phenoxypropanol and phenoxy butanol; ethers having at least 5 carbon atoms,preferably C₅₋₁₄-ethers, e.g. anisole and phenetole; nitrocellulose,cellulose ether, cellulose acetate; low odour petroleum distillates;turpentine; white spirits; naphtha; isopropylbiphenyl; terpene;vegetable oil; mineral oil; essential oil; and natural oil; and mixturesof any two or more thereof.

[0044] The composition may be prepared by mixing the nitrile polymer andliquid medium. Suitable mixing techniques are well known in the art, forexample agitation, ultrasonication or stirring of the components.

[0045] The nitrile polymer may be present in the composition in any formsuitable for application to the substrate, for example the form of adispersion, emulsion, suspension, solution or a combination thereof.

[0046] To achieve a particularly good dispersion additional dispersantsmay be added. Preferably the dispersant is a surfactant. Preferredsurfactants are anionic surfactants such as; sodium dodecyl sulphate,ammonium dodecyl benzene sulphonate, sodium nonoxynyl phosphate, sodiumdioctyl sulphosuccinate; nonionic surfactants such as alkyl phenolethoxylates, alkyl ethoxylates, polyoxyethylene polyoxypropylene blockcopolymers; cationic surfactants such as; dodecyl trimethyl ammoniumbromide, bis(2-hydroxyethyl)tallow amine; and amphoteric surfactantssuch as ammonium cocoaminopropionamide. The choice of dispersants willbe governed by many factors including: the nitrile polymer chosen andits physical/chemical properties; the amount of polymer to be dispersed;and the nature of the liquid medium. For an optimum dispersion it may benecessary to use a mixture of several dispersants.

[0047] The binder is preferably a polymeric or polymerisable binder,more preferably a water-soluble or water-dissipatable polymeric orpolymerisable binder optionally containing porous inorganic particlese.g. alumina (especially boehmite) or siliceous particles, especiallyparticulate amorphous precipitated silica having a calculated multimodalparticle size distribution wherein the particle sizes at the modes areless than 10 micrometers, as described in U.S. Pat. No. 5,804,293, andthe siliceous particles referred to in PCT/US96/19361, page 9, lines 21to 29 which are incorporated herein by reference thereto. Theseparticles improve absorbency of the substrate for inks, resulting inbetter wet and rub fastness properties for the substrate. Optionally theporous inorganic particles are incorporated into the substrate as acomponent of the binder.

[0048] Preferred water-soluble binders include starches, preferablyhydroxy alkyl starches, for example hydroxyethylstarch; celluloses, forexample cellulose, methylcellulose, hydroxyethylcellulose,hydroxypropylcellulose, hydroxyethyl methyl cellulose andcarboxymethlycellulose (and salts thereof) and cellulose acetatebutyrate; gelatin; gums, for example guar, xanthan gum and gum arabic;polyvinylalcohol; polyvinylphosphate; polyvinylpyrrolidone;polyvinylpyrrolidine; polyethylene glycol; hydrolysed polyvinylacetate;polyethylene imine; polyacrylamides, for example polyacrylamide andpoly(N,N-dimethyl acrylamide); acrylamide-acrylic acid copolymers;polyvinylpyridine; polyvinylphosphate; vinylpyrrolidone-vinyl acetatecopolymers; vinyl pyrrolidone-styrene copolymers; polyvinylamine;poly(vinyl pyrrolidonedialkylaminoalkyl alkylacrylates), for examplepoly vinylpyrrolidone-diethylaminomethylmethacrylate; acid-functionalacrylic polymers and copolymers, for example poly(meth)acrylic acid andcopolymers of (meth)acrylic acid and other (meth)acrylate monomers;amine-functional acrylic polymers and copolymers, for examplepolydimethylaminoethylmethacrylate; acid or amine functional urethanepolymers, preferably those containing dimethylolpropanoic acid and/orpendant or terminal polyethylene glycols; ionic polymers, especiallycationic polymers, for example poly (N,N-dimethyl-3,5-dimethylenepiperidinium chloride); polyesters, preferably those which carrywater-solubilising groups, especially acid groups, for examplepolyesters obtainable by polymerising a polyol withsodiosulphoisophthalic acid.

[0049] Preferred water-dissipatable binders are water-dissipatablepolymers, more preferably latex polymers, for example cationic,non-ionic and anionic styrene-butadiene latexes; vinyl acetate-acryliccopolymer latexes; acrylic copolymer latexes which carry quaternaryammonium groups, for example a polymethylacrylate trimethylammoniumchloride latex; and dispersions of poly(acrylate), poly(methacrylate),polyester, polyurethane or vinyl polymers and copolymers thereof. Thepolymer dispersions are preferably prepared by emulsion, suspension,bulk or solution polymerisation followed by dispersion into water.

[0050] The binder may comprise a single binder or comprise a mixture oftwo or more binders, especially the preferred binders described above.The binder may also be a Quikote™ coating material available from PPGIndustries Inc. Colour bleed in the resultant substrate can be reducedor even eliminated if the binder contains (1) water-soluble film-formingorganic polymer which is substantially free of onium groups, and (2) awater-soluble or water-dispersible onium addition polymer consistingessentially of onium-containing mer units. Preferably the weight ratioof the binder to the nitrile polymer is from 99:1 to 1:99, morepreferably from 80:20 to 20:80.

[0051] A preferred composition suitable for coating or impregnating thesubstrate comprises:

[0052] (a) from 0.01 to 99.99, more preferably 1 to 99.98, parts of thenitrile polymer;

[0053] (b) from 0 to 99.98 , more preferably 1 to 10, parts of a binder;and

[0054] (c) from 0.01 to 99.99, more preferably 0.1 to 50, parts of aliquid medium.

[0055] wherein all parts are by weight and the total number of parts(a)+(b)+(c)=100.

[0056] The media may also comprise other additives including, but notlimited to, silica gels, aluminas, antioxidants, UV absorbers, mordantsespecially cationic mordants more especially cationic polymers.

[0057] The composition for coating or impregnating the substrate ispreferably colourless, weakly coloured or white.

[0058] According to a second aspect of the invention there is provided acomposition comprising a water-dissipatable nitrile polymer having a Mnof less than 25,000 comprising 5 to 70% w/w of a nitrile monomer and aliquid medium.

[0059] The composition is preferably colourless or weakly coloured,preferably colourless. The liquid medium is preferably as describedabove in relation to the first aspect of the invention. Preferably theliquid medium used in the colourless or weakly coloured compositioncomprising the nitrile polymer comprises water, more preferably waterand a water-miscible organic solvent. Optionally it further comprises abinder more preferably a binder as described in the first aspect of thepresent invention.

[0060] Preferably a colourless or weakly coloured composition accordingto the aspect of the invention comprises:

[0061] (a) from 0.01 to 99.8 parts of a water-dissipatable nitrilepolymer having a Mn of less than 25,000 comprising 5 to 70% w/w ofnitrile monomers;

[0062] (b) from 0 to 99.7 parts of a binder;

[0063] (c) from 0.01 to 99.98 parts of organic solvent; and

[0064] (d) from 0.01 to 99.98 parts water;

[0065] wherein all parts are by weight and the total number of parts(a)+(b)+(c)+(d)=100.

[0066] According to a third aspect of the present invention there isprovided a process for printing an image on a substrate comprisingapplying thereto an ink containing a colorant by means of an ink-jetprinter such that the colorant, when situated on the substrate, is incontact with a water-dissipatable nitrile polymer having a Mn of lessthan 25,000 comprising 5 to 70% w/w of nitrile monomers.

[0067] Preferably the substrate is as preferred in the fist aspect ofthe invention. In this third aspect of the invention, an ink-jet printerpreferably applies the ink to the substrate in the form of droplets thatare ejected through a small orifice onto the substrate. Preferredink-jet printers are piezoelectric ink-jet printers and thermal ink-jetprinters. In thermal ink-jet printers, programmed pulses of heat areapplied to the ink composition of the third aspect in a reservoir bymeans of a resistor adjacent to the orifice, thereby causing the ink orthe colourless or weakly coloured composition to be ejected in the formof small droplets directed towards the substrate during relativemovement between the substrate and the orifice. In piezoelectric ink-jetprinters the oscillation of a small crystal causes ejection of the inkor the composition of the third aspect from the orifice. In WO 00/48938and WO 00/55089 a new form of piezoelectric technology is describedwhere ink is ejected from an ink ejection nozzle chamber utilizing anelectromechanical actuator connected to a paddle or plunger which movestowards the ejection nozzle of the chamber for the ejection of drops ofink from the ejection nozzle chamber.

[0068] Preferably the process of the third aspect of the presentinvention further comprises the step of applying the nitrile polymer tothe substrate by means of an ink-jet printer. The nitrile polymer ispreferably applied to the substrate before, during or after applicationof the ink to the substrate, more preferably before application of theink to the substrate.

[0069] The ink may be any ink suitable for application by an ink-jetprinter.

[0070] The colorant used in the ink is preferably yellow, magenta, cyanor black.

[0071] The colorant may be a single coloured component or a mixture ofcoloured components, for example it may be a mixture of different dyesand/or pigments. By using a mixture of different dyes as the colorantone may achieve greater flexibility in colour of the ink.

[0072] The colorant is preferably an anionic dye, more preferably acationic dye, especially a disperse dye. These preferences arise becausethe increase in light fastness is better with cationic dyes than anionicdyes, and disperse dyes are better than cationic and anionic dyes.Optionally the colorant is insoluble in the nitrile polymer, althoughpreferably the colorant is preferably soluble in the nitrile polymer.Suitable disperse dyes are soluble in organic solvents and insoluble inwater. Preferred disperse dyes are free from sulpho and carboxy groups.

[0073] Useful classes of colorants include anthraquinones,phthalocyanines, pyrrolines, triphenodioxazines, methines,benzodifuranones, coumarins, indoanilines, benzenoids, xanthenes,phenazines, solvent soluble sulphur dyes, quinophthalones, pyridones,aminopyrazoles, pyrollidines, styrylics and azoics. Examples ofpreferred azoics are monoazo, disazo and trisazo disperse dyes each, ofwhich are optionally metallised and solvent soluble dyes; especiallypreferred azoics contain heterocyclic groups. The Colour IndexInternational lists suitable disperse and solvent soluble dyes, examplesof which include Solvent Blue 63, Disperse Blue 24, Solvent Black 3,Solvent Black 35 and Disperse Red 60.

[0074] Further examples of disperse dyes are given in the Colour Index,3rd Edition, Volume 2, pages 2483 to 2741 and further examples ofsolvent soluble dyes are given in Volume 3, pages 3566 to 3647 and eachof these dyes is included herein by reference thereto.

[0075] The viscosity of the ink is preferably less than 20 cp, morepreferably less than 15 cp, especially less than 10 cp, at 20 °C.

[0076] Preferably the ink has been filtered through a filter having amean pore size less than 101 μm, more preferably less than 5 μm,especially less than 1 μm. In this way particulate matter that couldotherwise block the printer-head is removed.

[0077] A fourth aspect of the present invention provides a substrateasdescribed in the first aspect of the invention printed by means of aprocess as described in the third aspect of the invention.

[0078] Substrates of the present invention when printed provide sharpimages with excellent print quality and little if any bleed betweencolours printed side by side. Furthermore an image on the substrateshows good storage stability, wet fastness and fastness to both acidicand alkaline highlighter pens. In particular an image printed on thesubstrate shows excellent light-fastness.

[0079] The invention is further illustrated by the following Examples inwhich all parts are by weight.

EXAMPLE 1 Stage A—Preparation of Inks

[0080] Ink 1

[0081] C.I.Basic Red 1 (1 part)

[0082] 2-pyrrolidone (99 parts)

[0083] Ink 2

[0084] Dye of Formula (2) (0.15 parts)

[0085] tetrahydrofuran (99.85 parts)

[0086] Formula (2)

[0087] The dye of Formula (2) was prepared as described in Stage 2,Example 1 of WO 98/14523.

[0088] Ink 3

[0089] Direct Yellow 86 (2.3 parts)

[0090] 2-pyrolidone (97.7 parts)

Stage B—Preparation of Water-Dissipatable Acrylonitrile Polymer

[0091] Acrylonitrile Polymer 1-S/2-EHA/AN/MAA/AA=19.5/35/40/3.7511.25

[0092] Acrylonitrile Polymer Was Prepared as Follows: Materials Weight(g) De-ionised Water 250 Monomer Feed Styrene (“S”) 65.522-Ethylhexylacrylate (“2-EHA”) 97.2 Acrylonitrile (“AN”) 123.4Methacrylic Acid (“MAA”) 11.6 Acrylic Acid (“AA”) 3.85 Monomer ShotStyrene 7.28 2-Ethylhexylacrylate 10.8 Initiator Feed Ammoniumpersulphate (APS) 2.984 De-ionised water 72 Sodium lauryl sulphate 4.48Initiator Shot Ammonium persulphate 0.746 De-ionised water 18 Sodiumlauryl sulphate 1.12 Burn-up Co-initiator Ascorbic acid 2.243 De-ionisedwater 42.58 Burn-up Initiator t-Butyl hydrogen peroxide (70% solids)3.20 De-ionised water 41.62 Odour reducer Hydrogen peroxide solution(30% solids) 2.49

[0093] Procedure

[0094] The monomer shot was added to the water at 80° C. under anitrogen atmosphere with continuous stirring. After 5 minutes theinitiator shot was added to seed the polymerisation and the mixture wasstirred for a further 15 minutes before the monomer and initiator feedswere added over 90 minutes, maintaining the temperature of the reactionat 80-83° C. After addition of the monomer and initiator feeds werecomplete the stirring was continued at 80-83° C. for a further hour. Theresultant mixture was cooled to 50° C., at which point the burn-upco-initiator was added dropwise over 30 minutes. The burn-up initiatorwas added in 3 equal shots at 1, 10 and 20 minutes of the co-initiatoraddition. The mixture was stirred for a further 30 minutes beforehydrogen peroxide solution was added dropwise over 10 minutes. Theresultant mixture was cooled and filtered to give Acrylonitrile Polymer1 having a pH of 7, a solids content of 42%, a viscosity @20° C. of 32cps, a Mn (polystyrene equivalent) of 17,500 and a particle diameter of55 nm. Control Polymer (free from acrylonitrile (S/2-EHA/MAA/AA))Materials Charge (g) Initiator charge water 189 Nansa AS40  3.95 g in 10g water APS initiator charge  0.158 in 5 g water Monomer feed S 187.12-EHA 113.9 MAA  11.9 AA  3.95 Surfactant feed water  72.1 Nansa AS40 15.8 g in 50 g water Initiator feed APS  0.7 g in 70 g water

[0095] Procedure

[0096] The water (189 g) was added to a reactor and heated to 80° C.with continuous stirring under an atmosphere of nitrogen. The Nansa™AS40 (a non-ionic surfactant from _Albright and Wilson) (3.95 g) wasadded, followed by the APS initiator charge. 10% of the monomer feed wasadded and the mixture heated to 85° C. with continuous stirring for 15minutes. The monomer feed, surfactant feed and initiator feed were addedin parallel over 2 hrs maintaining temperature at 85° C. After 2 hrs theinitiator burn up was added and the temperature was maintained at 85° C.for 1 hour with agitation. The resultant mixture was cooled and filteredto give the control polymer having a 39% solids content and an averageparticle diameter of 80.5 nm.

EXAMPLE 1 TO 3 Under Printing with Acrylonitrile Polymer 1

[0097] Substrates were prepared by coating an aqueous solution ofAcrylonitrile Polymer 1 (42% solids content) or the Control Polymer toseparate sheets of Champion Datacopy paper using a K-bar #2. The sheetswere left to dry for 10 minutes. Inks 1 to 4 were we applied to thesheets and allowed to dry for 24 hours.

[0098] After drying for 24 hours, the dyed sheets were half covered andplaced in an HPUV accelerated indoor fadeometer. The dyed sheets wereexposed for the equivalent of three years based on the standard indoorconditions of 450 lux for 12 hours per day. After fading the sheets wereremoved and the reflected optical density of the unfaded and fadedportions of the sample measured in an X-Rite™938 spectrodensitometer.The percentage of reflected optical density lost was then calculatedusing the following equation in which ROD means reflected opticaldensity:${\% \quad {ROD}\quad {loss}} = {\frac{\left( {{{ROD}\quad {before}\quad {exposure}} - {{ROD}\quad {after}\quad {exposure}}} \right)}{{{ROD}\quad {before}\quad {exposure}}\quad} \times 100}$

[0099] A lower value for %ROD loss indicates higher lightfastness. Theresults are shown in Table 1.

[0100] A comparative sample was prepared where ink 1 was directly coatedonto Champion Datacopy paper using the K-bar without AcrylonitrilePolymer 1 being present. The sample was then faded under the sameconditions as above and the %ROD loss measured. Other comparativeexamples were performed in which the inks were applied directly to thepaper (i.e. no polymer was used). The results are shown in Table 1.TABLE 1 Sample 1 Polymer % ROD loss Ink 1 Acrylonitrile Polymer 1 35 Ink1 None 70 Ink 1 Control Polymer 66 Ink 2 Acrylonitrile Polymer 1 13 Ink2 No Polymer 76 Ink 3 Acrylonitrile Polymer 1 7 Ink 3 No Polymer 24

[0101] As can be seen from Table 1, the % ROD loss was much lower whenAcrylonitrile Polymer 1 was used compared to when no polymer was used ora polymer free from acrylonitrile was used.

1. A substrate for ink-jet printing with an ink containing a colorantwherein the substrate is coated or impregnated with a water-dissipatablenitrile polymer having a Mn of less than 25,000 comprising 5-70% w/w ofnitrile monomers and acid groups as water dispersing groupscharacterised in that the colorant in contact with thewater-dissipatable nitrile polymer exhibits enhanced light-fastness. 2.A substrate according to claim 1 wherein the acid groups are carboxylicacid groups.
 3. A substrate according to either claim 1 or claim 2wherein the water-dissipatable nitrile polymer has been obtained fromthe polymerisation of acrylonitrile and/or methacrylonitrile with one ormore olefinically unsaturated monomers having water dispersing groups,optionally in the presence of one or more olefinically unsaturatedmonomers which are free from water dispersing groups.
 4. A substrateaccording to any one of the preceding claims which is obtainable byimpregnating or coating with a composition comprising a nitrile polymerhaving a Mn of less than 25,000 comprising 5 to 70% w/w of a waterdissipatable nitrile monomer, a liquid medium and optionally a binder.5. A substrate according to claim 4 wherein the binder is awater-soluble or water-dissipatable polymeric or polymerisable binder.6. A substrate according to either claim 4 or claim 5 wherein the binderis a water-soluble or water-dissipatable polymeric or polymerisablebinder containing porous inorganic particles.
 7. A substrate accordingto any one of the preceding claims wherein the substrate is a coated oruncoated paper, overhead projector slide or a textile material.
 8. Acomposition comprising a water-dissipatable nitrile polymer having a Mnof less than 25,000 comprising 5 to 70% w/w of a nitrile monomer andacid groups as water dispersing groups with a liquid medium.
 9. Acomposition according to claim 8 comprising: (a) from 0.01 to 99.8 partsof a water-dissipatable nitrile polymer having a Mn of less than 25,000comprising 5 to 70% w/w of nitrile monomers and acid groups as waterdispersing groups; (b) from 0 to 99.7 parts of a binder; (c) from 0.01to 99.98 parts of organic solvent; and (d) from 0.01 to 99.98 partswater; wherein all parts are by weight and the total number of parts(a)+(b)+(c)+(d)=100.
 10. A process for printing an image on a substratecomprising applying thereto an ink containing a colorant by means of anink-jet printer such that the colorant, when situated on the substrate,is in contact with a water-dissipatable nitrile polymer comprising 5 to70% w/w of nitrile monomers and acid groups as water dispersing groups.11. A process according to claim 10, which further comprises the step ofapplying the nitrile polymer by means of an ink-jet printer.
 12. Aprocess according to either claim 10 or 11 wherein the substrate is asdescribed in any one of claims 1 to
 7. 13. A substrate printed by meansof a process as described in any one of claims 10 to 12.